Hypersensitive baboons will be exposed to sulfur dioxide, nitrogen dioxide, and a combination of the two gases to determine the effects of such exposure upon spontaneous release of histamine from circulating leukocytes during the course of the exposures, and from lung mast cells at termination of the exposure period; changes in antigen-antibody mediated release of mediators will be studied by allergen and anti-IgE challenge of sensitized and non-sensitized cells from gas-exposed and normal animals. Possible changes in membrane-bound enzyme function as a result of the exposure will be determined by assessing intracellular cyclic AMP levels in gas-exposed normal and hypersensitive animals compared to normal and hypersensitive animals breathing clean air. These studies will provide an insight into the possible mechanisms underlying clinically observed exacerbations in allergic symptoms in atopic and/or asthmatic individuals breathing polluted atmospheres, and may provide a more rational basis for management or treatment of such individuals.